The overall aim of the research is to further the understanding of the mental health consequences of the use of marijuana and other substances and of developmental patterns of involvement and cessation in the use of various drugs. The proposed epidemiological research is based on longitudinal data collected in adolescence and in young adulthood on a representative subsample of adolescents formerly enrolled in high school grades 10 and 11 in New York State in 1971-72. One adult follow-up was carried out in 1980 with 1,325 respondents 24-25 years old, 8 years after initial contact for adolescents who participated in an initial high school survey (N=1,081) and a complementary group of absentees (N=244) from the same schools. A second follow-up of the total group is planned for 1984, at ages 28-29, with field procedures identical to those followed in 1980. Data will be collected through personal interviews, averaging two hours in duration. Detailed retrospective life and drug histories will be collected as well as information from school records. Depressive symptomatology, physical health and psychological functioning will be assessed. The drugs inquired about include the following ten classes: cigarettes, alcohol, marijuana, psychedelics, heroin, other opiates, cocaine, and medical and nonmedical use of stimulants, sedatives and tranquilizers. Three activities are outlined in the proposal: (1) continued analyses of the health consequences of drug use based on the first adult follow-up in 1980, (2) implementation of the second follow-up in 1984, and (3) analyses of the additional longitudinal data. The specific objectives of the research are: (1) to examine patterns of involvement, regression, and cessation in drug use at the point in the life-cycle that spans the years from adolescence to young adulthood; (2) to identify the psychological precursors in adolescence of drug use in young adulthood; (3) to specify the mental health consequences of such use; (4) to investigate the interactive relationship between depressive mood and drug use from adolescence to adulthood; and (5) to identify the correlates and predictors of cessation of drug use in early adulthood.